Lens stack



FIG. 1 is a top perspective view of our new design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view and lacks shading thus indicating that the bottom surface is not claimed thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a front elevation view thereof; and,

FIG. 7 is a rear elevation view thereof.

Portions of the lens stack are shown in broken lines to illustrate unclaimed subject matter that forms no part of the claimed design.

The distal tabs are shown with symbolic breaks in its length. The appearance of any portion of the article between the break lines form no part of the claimed design. 

CLAIM We claim the ornamental design for a lens stack, as shown and described. 